itunes app downloads then not updating

Hi team,

I have not been able to find a solution to this issue via Google or the apple support community.

An iOS app update fails to complete its download. It is listed as "Done" in the download page that lists active downloads. However on the iTunes Apps Updates tab it remains flagged as "Downloading". The file remains in the "E:\Users\myName\Music\iTunes\iTunes Media\Downloads\appName.tmp" folder as download.app and Info.plist. I have left iTunes running for several hours and it does not update. When I restart iTunes and/or Win7, the app is there for updating and downloads again. Sometimes the second download works correctly, sometimes it takes several attempts over several days, and sometimes I get impatient and download on my iPhone (on the same network) and sync it to iTunes.

It happens approximately once a week on average, and only seems to happen to one app out of the 5 or so that download each session

Most recent failed downloads were

MS Word 1.6.1: Feb 18 and 21

YouTube 10.7.11524 Feb 24 and 25

And from files in the downloads folder, also

Calorie Counter: Feb 10 twice

4 Pics 1 Word Feb 9

Google Feb 13

I'm running

Win7 Pro SP1 64-bit, all patches applied, i7-3700, 16 GB

iTunes 64bit 12.1.1.4 (issue also occurred with prior versions)

I have tried reinstalling iTunes with no success.

Thanks in advance for any suggestions.